Lippincott-Raven Publishers. Volume 1(345) December 1997 pp

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1 Lippincott-Raven Publishers. Volume 1(345) December 1997 pp Cost Effectiveness and Quality of Life in Knee Arthroplasty [Symposium: The Insall Award] Lavernia, Carlos J. MD; Guzman, Jose F. MS, BE; Gachupin-Garcia, Andrea BS From the Division of Arthritis Surgery, Department of Orthopaedics and Rehabilitation, University of Miami, School of Medicine, Miami, FL. Supported by Howmedica. Reprint requests to Carlos J. Lavernia, MD, 1321 Northwest 14th Street, Suite 203, Miami, FL Outline Abstract MATERIALS AND METHODS RESULTS DISCUSSION References Graphics Table 1 Table 2 Fig 1 Fig 2 Fig 3 Fig 4 Abstract Few studies quantitate the cost of a quality well being as produced by arthroplasty surgery. The objective was to use the Quality of Well Being Index to calculate the cost per quality of well year in knee arthroplasty surgery. The difference in Quality of Well Being Index scores before and after the intervention was calculated and multiplied by the patient's life expectancy. The procedure cost was divided by this quantity resulting in the cost of a quality well year. One hundred patients underwent a primary knee arthroplasty. There were 30 males (average age, 62 years old) and 70 females(average age, 64 years old). The calculated costs per a quality well year were $30,695 (standard deviation

2 $90,883) at 3 months, $17,804 (standard deviation $25,888) at 6 months, $11,560 (standard deviation $11,874) at 1 year, and $6656 (standard deviation $3567) at 2 years postsurgery. Health economists consider an intervention costing less than $30,000 per quality of well year a bargain to society. Cost effectiveness of knee arthroplasty surgery compares favorably with other surgical interventions such as coronary artery bypass surgery ($5000 per quality of well year) and extremely favorable with medical treatments such as renal dialysis ($50, for the quality well year). Knee arthroplasty is a cost effective procedure and should be considered an appropriate investment by society. Arthroplasty surgery in one of the most successful surgical procedures for arthritis of the knee. Because of the current concerns about cost, knee arthroplasty surgery is considered by many healthcare providers and payers to be an expensive procedure.33 Impending rationing and Medicare reform could affect the delivery or the reimbursement of arthroplasty surgery significantly. Gill and Feinstein 11 performed a comprehensive review of every English language article published in the past 10 years on quality of life. More than 210 instruments are available to assess the change in the quality of life of a patient after a healthcare intervention.11 Some of these instruments are disease specific but most are global evaluations of the quality of life of a patient. Very few of these instruments allow the quantification of the dollar amount involved in obtaining or defining a quality well year. Gill and Feinstein 11 concluded that one of the most important issues in this evaluation was that most of these indices imposed a definition of quality of life to the patient. They suggested that quality of life is a unique personal perception in the way that an individual feels about their own health status. Few articles have been published assessing the effects of arthroplasty surgery on the quality of life of patients with arthritis.4,20,23,25,29,30,35,36 Rissanen et al 30 studied patients waiting for arthroplasty surgery in Finland using the Nottingham Health Profile to assess the change in quality of life after hip or knee arthroplasty surgery. Liang et al 23 assessed the methodologies that should be used when evaluating patient's quality of life but presented no data. Borstlap et al 4 assessed the effects of hip replacement in patients with osteoarthritis and rheumatoid arthritis in the Netherlands. Wiklund and Romanus 35 assessed the quality of life before and after arthroplasty surgery of the hip in Gothenburg, Sweden. Laupacis et al 20 assessed the change in quality of life after total hip replacements in patients in Canada. They used the Western Ontario and McMaster University Osteoarthritis Index and the Mactar Patient Preference Questionnaire to assess the effects of a surgical intervention on the hip. Wilcock 36 assessed the effects of hip replacement in older patients at 6 months using the Nottingham Health Profile. All these studies conclusively showed that arthroplasty is an effective and pain relieving procedure. However, only Laupacis et al 20 placed an actual dollar value to the quality of life produced by an arthroplasty procedure. Numerous orthopaedic indices that assess the outcome of patients who had arthroplasty are available and used in the literature. These orthopaedic rating scales have been used to

3 assess the pain relief and the functional issues of arthroplasty surgery. In knee replacement surgery these scores include the Knee Society Clinical Rating System and Hospital for Special Surgery Knee Rating System.1,5,6,14,15,31 Neither of these systems have been validated in construct or content. These indices, however, are widely accepted and used in the orthopaedic community and provide a familiar measure of pain and function to the orthopaedic community. Few instruments are available that quantitate the quality of life before and after a medical intervention and that will allow for the calculation of cost for quality adjusted life years. The Quality of Well Being Index was developed by Kaplan et al 16 and permits the evaluation of several different interventions and calculates the equivalent of well years produced. The Quality of Well Being Index defines a quality well year as a period of relatively pain free and high quality of life for a patient. It has been widely used in cystic fibrosis,26,27 noninsulin dependent diabetes,18 and several other disease processes to assess the differences between the genders.17 Construct validation and criterion validity have been performed on this index. The Quality of Well Being Index constitutes a relatively lengthy questionnaire that is divided into three scales: mobility scale, physical activity scale, and social activity scale. In addition, a symptom problem complex score is calculated based on the importance of different symptomatology and their effects on a patient's life. The index represents the patient's preference for a given health state relative to perfect health, on a scale from 0 to one, with a value of one being equivalent to perfect health and a value of 0 being equivalent to death. The authors' objective was to use the Quality of Well Being index to calculate the cost per quality adjusted life year on patients undergoing total knee arthroplasty surgery. MATERIALS AND METHODS All patients undergoing primary total knee arthroplasty surgery within the Division of Arthritis Surgery at the University of Miami were included in the study. All patients having arthroplasty undergo the same conservative care before surgical intervention. This includes the appropriate use of nonsteroidals (two different nonsteroidal antiinflammatory drugs for a period of 4 weeks each), weight loss, and the use of a cane preoperatively. The surgical intervention consisted of a knee arthroplasty using a Howmedica Duracon device (Rutherford, NJ). This knee device consists of CoCr femur and a CoCr cruciform tibial base plate and an all polyethylene patella. Each patient's quality of life was assessed preoperatively and at 3 months, 6 months, 1 and 2 years postoperatively using the Quality of Well Being Index. Procedures charges and monthly cost to charges ratios were provided by the hospital's chief financial officer. Procedure cost was obtained by dividing all hospital charges by the cost to charges ratio. The total costs then were calculated by adding all the surgical professional fees to the total hospital cost. Discounting was not incorporated in the quality well year calculations. The cost of a quality adjusted life year was calculated as follows: The preoperative Quality of Well Being score was subtracted from the postoperative Quality of Well Being

4 score at the various followup periods. In the time dependence analysis each assessment period was considered an end point. The calculated difference then is multiplied by the patient's life expectancy as obtained by standard life expectancy tables. This quantity represents the quality well years gained with the intervention, only the surgical professional fees were included in the study. All testing was performed at Columbia Cedars Medical Center. A quality adjusted life year is a year of relatively symptom free living that represents extreme satisfaction with the quality of life. The cost of a quality adjusted life year then was obtained by dividing the cost of the procedure by the expected quality well years. RESULTS One hundred patients underwent 127 primary knee arthroplasty procedures during the study. Twenty-seven patients had same day bilateral procedures. There were 30 males (average age, 62 years old) and 70 females (average age, 64 years old). Patient diagnoses included 82 osteoarthritis, 16 rheumatoid arthritis, one gouty arthritis, and one thromboembolism. Thirty-eight percent of the total patient population for this study was nonhispanic and 62% was Hispanic (Table 1). TABLE 1. Patient Demographics: (n = 100) Table 2 summarizes the procedure cost, average Quality of Well Being Index scores, and cost of quality adjusted life year for each assessment interval for single sided and bilateral cases.

5 TABLE 2. Results Summary DISCUSSION All arthroplasties are grouped in Diagnosis Related Groups 209 and 471. Orthopaedic surgery and in particular Diagnosis Related Group 209, currently are undergoing one of the most thorough economic scrutinies in its history. The main reason for this scrutiny is solely the total amount of federal dollars being spent on arthroplasty. Diagnosis Related Groups 209 and 471 had the highest expenditures ($4 billion) of any Diagnosis Related Group in The cost effectiveness of several high expenditure procedures such as arthroplasty has been questioned.3,7,12 As a result of this scrutiny a large reduction in the professional reimbursement for arthroplasty started in The fees of orthopaedic surgeons performing arthroplasty have been depreciated significantly.22 By 1997 it is expected that the reimbursement for a primary arthroplasty will be 30% less than the 1987 fees. From a health policy standpoint, Laupacis et al 21 divided cost outcome data into four groups. Interventions costing less than$20,000 were deemed very cost effective; interventions costing from$20,000 to $100,000 were considered moderately cost effective; intervention costing more than $100,000 were possibly effective but expensive; and inefficient medical interventions. This same group studying total hip arthroplasty determined the cost per quality adjusted life year to be $27,139 during the first year and $8031 during the first 3 years (Canadian dollars).19 The authors' results (data at 1 year) agree with the published calculations of Laupacis et al and clearly show the cost effectiveness of knee arthroplasty. The authors' calculated values compared favorably with other surgical interventions such as cardiac artery bypass surgery ($3500 per quality of well year) and extremely favorable with medical treatments such as renal dialysis ($40,300 for a quality well year),(fig 1).

6 Fig 1. Cost per quality adjusted life year for various medical interventions.34 PKU = phenylketonuria; TKR = total knee arthroplasty. Comparison of the cost effectiveness data between single sided and bilateral cases show that although, bilateral cases were significantly more expensive ($15,045, p =.001) there was no significant difference (p >.05) in the Quality of Well Being scores and cost per Quality Adjusted Year at any of the assessment intervals (Fig 2).

7 Fig 2. Cost per quality adjusted life years for single sided and bilateral cases. The data also show that the cost of a quality adjusted life year diminishes as a function of time (Fig 3). The large values calculated for the cost of a quality adjusted life year for the first 3 months may be because of the relative long rehabilitation process involved in knee replacement.

8 Fig 3. Average cost per quality adjusted life years versus assessment interval. Kaplan et al 16 reported on the natural decline of the quality of life of men and women as a function of age.figure 4 shows the quality of life curves for patients aged 60 to 85 years. As can be seen in this graph, there is a sharp drop in the quality of life for men and women in the age group of 60 to 85 years. This is the age group of most arthroplasty series. The natural plunging of the quality of life seen in this age group is significant. The effect of this natural process can be confounding in any cost effectiveness study in which quality of life is used. Despite this decline, the previously published data and the authors' data show a favorable outcome and the cost effectiveness of arthroplasty surgery.

9 Fig 4. Average versus average quality of well being index score regression fit 16 A major weakness of the study is that only patients with surgical arthritis who underwent an intervention were analyzed. There is a need for a prospective randomized study on the quality of life of patients with indications for arthroplasty. In this analysis, one group would be randomized to arthroplasty whereas the other group would be randomized to nonsurgical care. Considering the natural decrease in the quality of life because of age, this type of study may provide evidence on the slowing down of their decline by arthroplasty. Knee arthroplasty is a cost effective procedure and compares most favorably with other medical and surgical interventions. There is an important time dependence on the cost of the quality well year in knee arthroplasty and the patient population that has arthroplasty has a naturally occurring decrease in quality of life. References 1. Andersson G: Hip assessment: A comparison of nine different methods. J Bone Joint Surg 54B: , [Context Link] 2. Andrykowski MA, Altmaier EM, Barnett RL, et al: The quality of life in adult survivors of allogeneic bone marrow transplantation. Transplantation 50: , Bibliographic Links Library Holdings 3. Bodenheimer T, Grumbach K: Paying for health care. JAMA 272: , [Context Link] 4. Borstlap M, Zant JL, Van Soesbergen M, et al: Effects of total hip replacement on quality of life in patients with osteoarthritis and in patients with rheumatoid arthritis. Clin Rheumatol 13:45-50, Bibliographic Links Library Holdings [Context Link] 5. D'Aubigné RM, Postel M: Functional results of hip arthroplasty with acrylic prosthesis. J Bone Joint Surg

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